﻿let map = new Map([["a", 1], ["b", 2]]);
let mapIterator = map[Symbol.iterator]();
console.log(mapIterator.next().value); // ["a", 1]
console.log(mapIterator.next().value);
console.log(mapIterator.next().value);
let set = new Set([1, 2, 3]);
let setIterator = set[Symbol.iterator]();
console.log(setIterator.next().value); // 1